Unit 3Organic Chemistry

Unit 3 Organic Chemistry

Chemistry 2202

Introduction

Organic Chemistry is the study of the molecular compounds of carbon.eg. CH4 CH3OH CH3NH2

Organic compounds exclude oxides of carbon and ions containing carbon.ie. CO, CO2, KCN, CaCO3

are NOT organic compounds!!

History of Organic Chemistry

Organic chemistry can be traced back to ancient times when medicine men extracted chemicals from plants and animals to treat members of their tribes

Organic chemistry was first defined as a branch of modern science in the early 1800's by Jon Jacob Berzelius

Berzelius believed in Vitalism - organic compounds could only originate from living organisms through the action of some vital force

organic compounds originate in living or once-living matter

inorganic compounds come from "mineral" or non-living matter

In 1828, Friedrich Wöhler discovered that urea - an organic compound - could be made by heating ammonium cyanate (an inorganic compound).

NH4OCN(aq) (NH2)2CO(s)

inorganic organic

organic chemistry branched into disciplines such as polymer chemistry, pharmacology, bioengineering and petro-chemistry

98% of all known compounds are organic

The huge number of organic compounds is due mainly to the ability of carbon atoms to form stable chains, branched chains, rings, branched rings, multiple rings, and multiple bonds (double and triple bonds) to itself and to many other non-metal atoms.

Sources of Organic Compounds

1. Carbonized Organic Matter- fossil fuels such as coal, oil, and

natural gas - basis for the petrochemical industry

2. Living Organisms eg: - penicillin from mold

- ASA from the bark of a willow tree

3. Invention

- antibiotics, aspirin, vanilla flavoring, and heart drugs are manufactured from organic starting materials

- plastics

Structural Isomers

Structures that have the same molecular formula but different structural formulas are called structural isomers

eg. C4H10

Practice: Draw all structural isomers of C5H12 and C6H14

Structural Isomers

structural isomers have the same chemical formula but have different chemical and physical properties.

Classifying Organic Compounds

Organic Compounds

HydrocarbonsHydrocarbonDerivatives

hydrocarbons consist of carbon and hydrogen atoms only

eg. Methane - CH4 hydrocarbon derivatives have one

or more hydrogen atoms replaced by another nonmetallic atom

eg. bromomethane - CH3Br

methanol - CH3OH

Hydrocarbons

AliphaticHydrocarbons

Aromatic Hydrocarbons(benzene based)

AlkAnes

AlkEnes

AlkYnes

aliphatic hydrocarbons have carbon atoms bonded in chains or rings with only single, double, or triple bonds

aromatic hydrocarbons contain at least one 6 carbon benzene ring

Aliphatic Hydrocarbons

1. AlkanesAlkanes are hydrocarbons that have

only single bonds between carbon atoms

general formula CnH2n+2

eg. C3H8 C6H14

IUPAC prefixes

Prefix # of carbon atoms

meth 1

eth 2

prop 3

but 4

pent 5

hex 6

hept 7

oct 8

non 9

dec 10

Complete this table for the first 10 alkanes

methane CH4

ethane

propane

A series of compounds which differ by the same structural unit is called a homologous series

eg. each successive member of the alkanes increases by CH2

Representing Alkanes (4 ways)

1. Structural formulas

eg. propane

H – C – C – C – H

HHH

HHH

Hydrogen atoms may be omitted from structural formulas

eg. propane

– C – C – C –

2. Condensed Structural Formula

eg. propaneCH3-CH2-CH3

3. Line Structural Diagrams

eg: propane

(the endpoint of each segment is a carbon atom)

4. Expanded Molecular Formulas

eg. propane

CH3CH2CH3

Alkyl Groups

An alkyl group has one less hydrogen than an alkane.

General Formula: CnH2n + 1

To name an alkyl group, use the prefix to indicate the # of carbon atoms followed by the suffix –yl

eg. -C7H15 heptyl

Alkyl Groups

methyl -CH3

ethyl -C2H5 or -CH2CH3

propyl -C3H7 or -CH2CH2CH3

Alkyl Groups

Branched alkanes are alkanes that contain one or more alkyl groups

eg.

Naming Branched Alkanes

1. Find the longest continuous chain of carbons and name it using the alkane name. This is the parent chain.

2. Number the carbons in the parent chain starting from the end closest to branching. These numbers will indicate the location of alkyl groups.


3. List the alkyl groups in alphabetical order. Use Latin prefixes if an alkyl group occurs more than once. (di = 2, tri = 3, tetra = 4, etc.)

4. Use a number to show the location of each alkyl group on the parent.


5. Use commas to separate numbers, and hyphens to separate numbers and letters.


eg.

7 6 5 4 3 2 1

ethyl

methyl

4-ethyl-3-methylheptane


Practice:p. 336 - 339 #’s 5 - 11

Alkenes and Alkynes

saturated compounds contain only single bonds between carbon atoms

eg. alkanessaturated compounds have the

maximum number of hydrogen atoms bonded to carbon atoms

Alkenes and Alkynes

unsaturated compounds contain double or triple bonds between carbon atoms

eg. alkenes and alkynes

Alkenes and Alkynes

General Formulas:

AlkenesCnH2n

AlkynesCnH2n - 2

Naming Alkenes and Alkynes

1. Name the longest continuous chain that contains the double/triple bond. Use the smallest possible number to indicate the position of the double or triple bond.


2. Branches are named using the same rules for alkanes. Number the branches starting at the same end used to number the multiple bond.


p. 347 #’s 17 - 19p. 354 #’s 28 & 29

Cyclic Hydrocarbons

Pp. 356 – 358questions 30 & 31

cyclopentane

methylethyl

1-ethyl-3-methylcyclopentane

3-ethyl-1-methylcyclopentane

1

2

3

methyl

1,2,3,4-tetramethylcyclohexane

Aromatic Compounds

Aromatic hydrocarbons contain at least one benzene ring.

The chemical formula for benzene, C6H6 , was determined by Michael Faraday in 1825.

Structural formula was determined by August Kekulé in 1865.

Aromatic Compounds

benzene ring consists of six carbon atoms, each of which is bonded to a hydrogen atom (Try to draw this!!)

C6H6 can be drawn with alternating single and double bonds.

Aromatic Compounds

While C=C double bonds are shorter than C-C single carbon bonds, x-ray crystallography shows that all six C-C bonds in benzene are the same length.

Benzene molecules behave like alkanes in chemical reactions, not like the alkenes

Aromatic Compounds

Kekulé thought benzene could exist in two forms and used the idea of resonance to explain its structure.

The resonance structure is an average of the electron distributions.

Aromatic Compounds

or

Aromatic Compounds

bonding electrons that were thought to be in the double bonds are delocalized and shared equally over the 6 carbon atoms

the bonds in benzene are like “1 ½” bonds – somewhere between single and double.

Naming Aromatic Compoundsan alkyl benzene has one or more H

atoms replaced by an alkyl group.name the alkyl groups, using

numbers where necessary, followed by the word benzene.

Aromatic Compounds

methylbenzene

propylbenzene

ethylbenzene

Aromatic Compounds

1,3-dimethylbenzene

1,4-dimethylbenzene

1,2-dimethylbenzene

Aromatic Compounds

ortho- means positions 1 and 2 and is represented by an italicized "o"

meta- means positions 1 and 3 and is represented by an italicized "m"

para- means positions 1 and 4 and is represented by an italicized "p"

Aromatic Compounds

m-dimethylbenzene

p-dimethylbenzene

o-dimethylbenzene

Aromatic Compounds

Benzene is treated as a branch if it is not attached to the terminal carbon of an alkyl group

Benzene as a branch is called phenyl

Aromatic Compounds

CH2

CH2

CH3

CH3CHCH3

propylbenzene2-phenylpropane

Aromatic Compounds

CH3CHCHCH2CH2CH3

CH2

CH3

Aromatic Compounds

CH3CHCHCH2CHCH2CH2CH3

CH2

CH2

CH3

CH3

Aromatic Compounds

p. 361 #’s 32 – 35

Hydrocarbons Practice

pp. 363, 364

#’s 4 – 9Test!!

Hydrocarbon Derivatives

Hydrocarbon Derivatives have one or more H atoms replaced by another nonmetallic atom

Types of derivatives:carboxylic acidsorganic halidesesters

alcoholsethersaldehydesketones


A functional group is the reactive group of atoms that gives a family of derivatives its distinct properties.

The general formula for a derivative is

R - functional group

where R stands for any alkyl group.

Bonded to


eg. ALCOHOLS R-OH

ethanol C2H5OH

propanol C3H7OH

CARBOXYLIC ACIDS R-COOH

ethanoic acid CH3COOH

propanoic acid C2H5COOH

hydroxyl group

carboxyl group


Types of derivatives (See p. 378)Alcohols – pp. 386 - 388Ethers – pp. 394 – 396Aldehydes & Ketones – pp. 402,403Carboxylic Acids – pp.405, 406Alkyl Halides – pp. 390, 391Esters – pp. 410, 411

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Unit 3Organic Chemistry